1. Field of the Invention
The present invention relates to a magneto-optical recording method and a magneto-optical recording medium for use in the magneto-optical recording method. More particularly, this invention relates to a magneto-optical recording method for recording optical information in an overwrite mode in an magneto-optical recording medium, reproducing recorded information and erasing the same with application of a laser beam thereto.
2. Discussion of Background
Conventional magneto-optical recording methods have a problem in that speedy information recording cannot be carried out because of the necessity for three steps of erasing, recording, and checking when information is recorded. The following overwrite systems have been proposed in order to solve this problem:
(i) Magnetic-field Modulation System
In this system, recording is performed by reversing the polarity of a magnetic field applied at high speed, while the intensity of a laser beam applied is maintained constant, in accordance with the information to be recorded, as disclosed in Japanese Laid-Open Patent-Applications 63-204532 and 63-76135. As mentioned above, in this system, the polarity of the magnetic field has to be reversed at high speed, so that the magnetic field for recording information has to be generated at a position away from the surface of a recording medium. For the generation of such a magnetic field, a large power is necessary. As a result, it is difficult to record the information at high frequency. A method of setting a magnetic head in close proximity to the surface of the medium has also been proposed. However, this method negates the inherent merit of the optical disc, that is, non-contact information recording.
(ii) Exchange Bonding Two-layer Films System
This system is directed to the accomplishment of overwriting by use of exchange bonding between two recording layers which consist of an amorphous alloy of a rare earth metal and a transition metal, as disclosed, for instance, in Japanese Laid-Open Patent Application 62-175948. More specifically, a magneto-optical recording medium comprising a recording layer consisting of TbFe and an auxiliary layer consisting of TbFeCo is employed. Overwriting is accomplished by initializing the recording medium and then applying thereto an external magnetic field and laser beams with different powers. This system, however, has a problem in that a large magnetic field is necessary for the initialization of the recording medium.